Re: [PATCH] PCI: endpoint: functions/pci-epf-test: Enable picking DMA channel by name

Rob Herring
2020-05-07T21:42:40Z

On Fri, May 01, 2020 at 09:20:08AM -0700, Alan Mikhak wrote:
> From: Alan Mikhak <alan.mikhak@sifive.com>
>
> Modify pci_epf_test_init_dma_chan() to call dma_request_channel() with a
> filter function to pick DMA channel by name, if desired.
>
> Add a new filter function pci_epf_test_pick_dma_chan() which takes a name
> string as an optional parameter. If desired name is specified, the filter
> function checks the name of each DMA channel candidate against the desired
> name. If no match, the filter function rejects the candidate channel.
> Otherwise, the candidate channel is accepted. If optional name parameter
> is null or an empty string, filter function picks the first DMA channel
> candidate, thereby preserving the existing behavior of pci-epf-test.
>
> Currently, pci-epf-test picks the first suitable DMA channel. Adding a
> filter function enables a developer to modify the optional parameter
> during debugging by providing the name of a desired DMA channel. This is
> useful during debugging because it allows different DMA channels to be
> exercised.
>
> Adding a filter function also takes one step toward modifying pcitest to
> allow the user to choose a DMA channel by providing a name string at the
> command line when issuing the -d parameter for DMA transfers.

This mostly looks fine, but needs to be part of a series giving it a
user.

> Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
> ---
> drivers/pci/endpoint/functions/pci-epf-test.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 60330f3e3751..043916d3ab5f 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -149,10 +149,26 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
> }
>
> /**
> - * pci_epf_test_init_dma_chan() - Function to initialize EPF test DMA channel
> - * @epf_test: the EPF test device that performs data transfer operation
> + * pci_epf_test_pick_dma_chan() - Filter DMA channel based on desired criteria
> + * @chan: the DMA channel to examine
> *
> - * Function to initialize EPF test DMA channel.
> + * Filter DMA channel candidates by matching against an optional desired name.
> + * Pick first candidate channel if desired name is not specified.
> + * Reject candidate channel if its name does not match the desired name.
> + */
> +static bool pci_epf_test_pick_dma_chan(struct dma_chan *chan, void *name)
> +{
> + if (name && strlen(name) && strcmp(dma_chan_name(chan), name))

Doesn't this cause warning with 'name' being void*?

> + return false;
> +
> + return true;
> +}
> +
> +/**
> + * pci_epf_test_init_dma_chan() - Helper to initialize EPF DMA channel
> + * @epf: the EPF device that has to perform the data transfer operation
> + *
> + * Helper to initialize EPF DMA channel.
> */
> static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
> {
> @@ -165,7 +181,7 @@ static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
> dma_cap_zero(mask);
> dma_cap_set(DMA_MEMCPY, mask);
>
> - dma_chan = dma_request_chan_by_mask(&mask);
> + dma_chan = dma_request_channel(mask, pci_epf_test_pick_dma_chan, NULL);
> if (IS_ERR(dma_chan)) {
> ret = PTR_ERR(dma_chan);
> if (ret != -EPROBE_DEFER)
> --
> 2.7.4
>